Question 5
QUESTION 5
a) Ammonia is manufactured industrially by the reaction between nitrogen gas and
Hydrogen gas.
(i) State one major source of:
I. nitrogen;
II. hydrogen.
(ii) Write a balanced chemical equation for the reaction.
(iii) State two conditions necessary for a high yield of ammonia;
(iv) Give two uses of ammonia. [8 marks]
(b) (i) List the major product(s) of each of the following reactions:
(I) burning carbon in limited air;
(II) heating carbon with calcium at high temperature;
(III) heating carbon with concentrated trioxonitrate (V) acid.
(ii) State two properties of carbon (IV) oxide that makes the gas suitable for use in a fire extinguisher.
[6 marks]
(c) (i) State the method of collecting gases which are denser than air.
(ii) Give two example of gases that could be collected by the method stated in 5(c)(i).
(iii) Name two gases that could be used to perform the fountain experiment.
(iv) State the property of the gases that makes them suitable for the experiment mentioned in 5(c)(iii).
[6 marks]
(d) (i) State two sources of air pollution.
(ii) Suggest two ways of reducing air pollution in our cities.
(iii) Mention one source of water pollution. [5 marks]
Observation
This question was popular among the candidates and their performance in the question was above average.
In part (a), majority of the candidates could not write a balanced chemical equation for the reaction. However, they were able to give two uses of ammonia.
In part (b), majority of the candidates listed the major product(s) when carbon is burnt in limited air and when carbon is heated with concentrated trioxonitrate (V) acid.
In part (c), majority of the candidates could state the method of collecting gases which are denser than air.
In part (d), majority of the candidates stated two sources of air pollution, and also suggested two ways of reducing air pollution in our cities.
The expected answers include:
(a) (i) - (fractional distillation of)liquid air
II - natural gas / water gas
(ii) N2(g) + 3H2(g) 2NH3(g)
(iii) - high pressure/200 - 250 atmospheres
- high temperature/450o – 500oC
- catalyst of finely divided iron
(iv) - in manufacture of plastics
- used in treating insect stings
- As a precipitating agent
- manufacture of HNO3
- manufacture of Na2CO3(by solvay process)
- used to soften (temporary) hardwater
- used as a refrigerant (cooling agent)
- to manufacture nitrogenous fertilizers
- used in laundry to remove stains
- as domestic cleaner to neutralize sweat
(b) (i) Carbon (II) oxide / CO
II. Calcium carbide / CaC2
III. Nitrogen (IV) oxide / NO2
Carbon (IV) oxide / CO2
(ii)- it is denser / heavier than air
- does not support combustion
(c) (i) downward delivery / upward displacement of air
(ii) - chlorine / (Cl2)
- hydrogen chloride / HCl
- carbon (IV) oxide / CO2
- sulphur (IV) oxide / SO2
- nitrogen (IV) oxide / NO2
- nitrogen (1) oxide/N2O
- nitrogen (II) oxide/NO
- hydrogen sulphide/H2S
- oxygen/O2
- sulphur (VI) oxide/SO3
(iii) - Ammonia
- hydrogen chloride
- Sulphur (IV) oxide
(iv) high solubility/readily/very soluble
(d) (i) - chemical warfare
- freons
- aerosols/smoke/fog/harmattan/fumes/dust/haze
- biological, agricultural and industrial activities
- forest fire
- products of combustion from factories
- fumes from exhaust
- sewage
- combustion from homes and factories
- volcanic eruption
(ii) - by siting factories far from residential areas
- treatment of effluents from the factories
- introduction of catalytic converters in cars
- proper monitoring of equipment
- educating/enlightening/creating awareness on the dangers of pollution
- monitoring of treatment of industrial waste by environmental agencies
- enactment of antipollution laws
(iii) - oil spillage
- animal waste
- effluent from industrial waste
- sewage disposal into water bodies
- chemicals from man’s activities
- agricultural activities
- domestic waste
- waste from hospitals
- radioactive waste
- acid rain